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“ Rate and distance fairness in OBS networks ”

Tananun Orawiwattanakul, Yusheng Ji

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Topics

• Optical Burst Switching (OBS) Networks

• Rate and Distance Fairness Preemption (RDFP)

• Simulation results

• Future works

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First OBS commercial product (2006)

Matisse Networks' EtherBurst™ is the world's first optical burst switch, purpose-build for scaling metro and campus networks from 10 to 640 gigabits-per-second (Gbps).

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Optical Burst Switching (OBS)

OEO

OOO

OEO

OOO

OEO

OOOData Burst (DB)

BCP

Offset = T Offset = T-D Offset = T-2D

Ingress edge

switch

Egress edge

switch

IP/ATM/GbE IP/ATM/GbE

OBS core network

Control channel

Data channelBurst

AssemblyBurst

De-assembly

5

DB4

Data ChannelsDB1

DB3

DB2

Time

Control Channels

C1 C2

C3

C4

T1 T2 T3 T4 T5

Offset Time1

Offset Time4

Offset Time1

Offset Time3

Offset Time2

C5DB5

Offset Time5

No Buffer -> High LossesVoid ->Network cannot be fully utilized

Challenge of OBS

DB

C

Data Burst

Burst Control Packet

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Rate Fairness

E1E1

C1C1

E2E2

Flow1 – 8 Gbps

Flow2 – 4 Gbps

E3E310 Gbps

‘Rate fairness’ refers to the fair bandwidth allocation (FBA) for each connection according to its offered rate and available bandwidth in the network.

The fair rate of flow 1 and flow 2 is 5 Gbps. It’s NOT FAIR!!! for me.

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Distance fairness

S4 S5S3

S1 S6

S7 S8S2

Path of Flow 1

Path of Flow 2

‘Distance fairness’ refers to the fair performance in terms of loss which respects to hop counts between the source and destination.

The loss probability of long-path flow tends to be higher than that of short path flow.It’s NOT FAIR!!! for me.

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Rate and Distance Fairness Preemption (RDFP)

Provide both “Rate and Distance fairness” in OBS networks.

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Rate and Distance Fairness Preemption (RDFP)

1. Allocate bandwidth to each flow according to the max-min fairness.

2. If any of the connections send the input traffic higher than their optimum fairly allocated bandwidth, the RDFP scheme can protect and prevent well-behaved connections from being degraded by misbehavior of other flows (rate fairness).

3. In the meantime, RDFP also balances the loss probability of bursts with different number of hops between the source and destination (distance fairness) for transmitted traffic amounts under the max-min rate.

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IngressEdge Switch

EgressEdge Switch

Core Switch 1

Core Switch 2

Core Switch N

Flow id

OriginalArrival Rate

Optimal Fairly

Allocated Bandwidth

i Ai Ti

RDFP: Control Plane

FBCP FBCPAi

BBCPBBCPTi

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Rate Fairness Preemption (RFP)

RDFP: Burst Marking

Time

Input RateIngress

Edge Switch

Flow id

OriginalArrival Rate

Optimal Fairly

Allocated Bandwidth

i Ai Ti

when Ai ≤ Ti, all bursts are marked as “Under-rate bursts (HIGH PRIORITY)”

Ti

Ai

Under-rate bursts (HIGH PRIORITY)

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Rate Fairness Preemption (RFP)

RDFP: Burst Marking

Time

Input RateIngress

Edge Switch

Flow id

OriginalArrival Rate

Optimal Fairly

Allocated Bandwidth

i Ai Ti

Ti

Ai

when Ai > Ti bursts are marked as

“Over-rate bursts (LOW PRIORITY)” with probability Pi-O = (Ai – Ti)/ Ai“Unver-rate bursts (HIGH PRIORITY)” with probability Pi-U = 1- Pi-O

Over-rate bursts (LOW PRIORITY)

Under-rate bursts (HIGH PRIORITY)

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When contention occurs in core networks, the “Under-rate (HIGH PRIORITY)” bursts can preempt an original scheduled channel

from “Over-rate (LOW PRIORITY)” bursts with different flow ids.

DB4

Data ChannelsDB3

DB2

Time

Control Channels

C2

C3

C4

T2 T3 T4 T5

Offset Time1

Offset Time1

Offset Time1

C5DB5

Offset Time5 Under-rate Burst

DB5DB1

C1

T1

Offset Time1

Over-rate Burst

RDFP: Rate fairness preemption policy

If no original scheduled over-rate burst -> determine the DISTANCE FAIRNESS preemption policy.

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When contention occurs in core networks, the “Under-rate (HIGH PRIORITY)” bursts can preempt an original scheduled

channel from bursts with lower of I.

DB4

Data ChannelsDB3

DB2

Time

Control Channels

C2

C3

C4

T2 T3 T4 T5

Offset Time1

Offset Time1

Offset Time1

C5DB5

Offset Time5 Under-rate Burst

DB5DB1

C1

T1

Offset Time1

Under-rate Burst with Lower I

RDFP: Distance fairness preemption policy

I = No of sucessful hops – Weight * (No. of remaining hops)

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Simulation networks

CoreSwitch 1

CoreSwitch 1

CoreSwitch 2

CoreSwitch 2

CoreSwitch 3

CoreSwitch 3

CoreSwitch 4

CoreSwitch 4

CoreSwitch 5

CoreSwitch 5

CoreSwitch 6

CoreSwitch 6

CoreSwitch 7

CoreSwitch 7 Edge

Switch 2Edge

Switch 2

EdgeSwitch 3

EdgeSwitch 3

EdgeSwitch 4

EdgeSwitch 4

EdgeSwitch 5

EdgeSwitch 5

EdgeSwitch 6

EdgeSwitch 6

EdgeSwitch 7

EdgeSwitch 7

EdgeSwitch 1

EdgeSwitch 1

The network consists of 42 flows: 3-hop flows = 14 flows, 4-hop flows = 14 flows, and 5-hop flows = 15 flows.

No. of data wavelength = 16

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RDFP: simulation results

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.05 0.06 0.07 0.08

The normalized sending rate of each 5-hop flow

Bur

st lo

ss p

roba

bilit

y 3-HOP4-HOP5-HOP

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.05 0.06 0.07 0.08The normalized sending rate of each 5-hop flow

Bu

rst

loss

pro

bab

ility 3-HOP

4-HOP5-HOP

Normalized rate 1 = 16 Gbps.

Input rate of each 3-hop and 4-hop flow = 0.05.

Input rate of each 5-hop = 0.05-0.08.

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Future works

• Extensively study the performance of TCP in RDFP-OBS based network.

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Q & A

Thank you